Liam Biesty was looking forward to his junior season. He played well on Poly Prep’s varsity squad a year ago and figured to be a key player for the Blue Devils.

Best of all, he was hoping to improve under the watchful eye of his older brother, Sean, a volunteer assistant with the team.

But that changed on Nov. 17, when Sean, 21, was involved in a serious car accident after Poly had scrimmaged Bishop Loughlin and he dropped Liam off at their Bay Ridge home. The crash left Sean in a coma and Liam without his most trusted teacher.

“He taught me everything I know,” said Liam, 16, before 4-2 Poly Prep faced New Utrecht in the Monsignor King Tournament yesterday. “I’m like his protege. When I was younger, all we did was play basketball, so after this happened, I really didn’t want to play anymore.”

He changed his mind soon after, though.

“I talked to my brother and even though he can’t really react, I really thought he would want me to keep going,” said Liam of Sean, who is slowly improving but who remains in a coma. “Sean wasn’t able to do everything he wanted to when he was in high school because he blew out his knee his senior year, so I know that nothing would make him happier than to see me succeed.”

Which is what he has done. The six-foot Biesty, who also plays soccer and baseball and kicks for the football team, is Poly’s starting shooting guard and its second-leading scorer at 15 ppg – much to his coach’s delight.

“He’s a tough kid,” said Bill McNally, who also coached Sean when he played basketball at Poly. “But this was a huge test and he’s handled everything as well as anyone could have.”

So has the rest of the team. Sean, a student at St. Joseph’s in Brooklyn, not only helped out at Poly, but also coached at McNally’s summer camp, which many of the players attend.

“He didn’t just work out with me,” Liam said. “He helped everyone on the whole team, so all of us felt it.”

Which made the loss that much greater, according to the coach.

“They all know him very well,” McNally said. “Everyone is close to him and we’ve all grown from this. Sean’s a big part of what we do. He’s not out of the woods yet, but he’s getting better, and, hopefully, he’ll be back on the bench, watching us again soon.”

When he does, he’ll likely see a different team.

“It’s definitely changed all of us,” Biesty said. “We’re more grateful for everything we have.”